<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
</head>
<body>
<script>
   window.alert("你好");
    alert("很好");
    console.log("今天是");
    console.warn("星期五");
    console.error("天气很好");
    document.write("今天下雪了");
</script>
</body>
</html>